Baroreflex responses to acute changes in blood volume in humans

C. A. Thompson, D. L. Tatro, D. A. Ludwig, V. A. Convertino

Research output: Contribution to journalArticle

69 Scopus citations

Abstract

To test the hypothesis that acute changes in plasma volume affect the stimulus-response relations of high- and low-pressure baroreflexes, eight men (27-44 yr old) underwent measurements for carotid-cardiac and cardiopulmonary baroreflex responses under the following three volemic conditions: hypovolemic, normovolemic, and hypervolemic. The stimulus-response relation of the carotid-cardiac response curve was generated using a neck cuff device, which delivered pressure changes between +40 and -65 mmHg in continuous steps of 15 mmHg. The stimulus-response relationships of the cardiopulmonary baroreflex were studied by measurements of forearm vascular resistance (FVR) and peripheral venous pressure (PVP) during low levels of lower body negative pressure (0 to -20 mmHg). Altered vascular volume had no effect on response relations of the carotid-cardiac baroreflex but did alter the gain of the cardiopulmonary baroreflex (-7.93 ± 1.73, -4.36 ± 1.38, and -2.56 ± 1.59 peripheral resistance units/mmHg for hypovolemic, normovolemic, and hypervolemic, respectively) independent of shifts in baseline FVR and PVP. These results indicate greater demand for vasoconstriction for equal reductions in venous pressure during progressive hypovolemia; this condition may compromise the capacity to provide adequate peripheral resistance during severe orthostatic stress. Fluid loading before reentry after spaceflight may act to restore vasoconstrictive capacity of the cardiopulmonary baroreflex but may not be an effective countermeasure against potential postflight impairment of the carotid-cardiac baroreflex.

Original languageEnglish (US)
Pages (from-to)R792-R798
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume259
Issue number4 28-4
StatePublished - Jan 1 1990

Keywords

  • arterial pressure
  • blood flow
  • cardiopulmonary baroreflex
  • carotid-cardiac baroreflex
  • lower body negative pressure
  • plasma renin activity
  • vasopressin
  • venous pressure

ASJC Scopus subject areas

  • Physiology

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    Thompson, C. A., Tatro, D. L., Ludwig, D. A., & Convertino, V. A. (1990). Baroreflex responses to acute changes in blood volume in humans. American Journal of Physiology - Regulatory Integrative and Comparative Physiology, 259(4 28-4), R792-R798.